1. Field of the Invention
The invention relates to a laser device having at least one gas-purged laser resonator which is arranged in a purging gas circuit which has upstream of the laser resonator both a low pressure generator for generating a purging gas excess pressure in the purging gas circuit and, between the low pressure generator and the laser resonator, a cleaning device for cleaning the purging gas.
2. Description of Related Art
Such a laser device having a gas-purged laser resonator is disclosed, for example, in U.S. 2003/0227957 A1.
Material processing requires lasers with high power and good beam quality which have a high level of stability over a long period of time. A possible source which can lead to instabilities during laser operation are occurrences of contamination (particles, moisture, organic compounds) in the laser device. Contamination may be deposited in the laser resonator and in the pump unit on components, such as, for example, mirrors and lead to wear or cause disruptions so that the beam quality or the power is reduced during operation. This can be prevented or minimised by purging the laser resonator and the pump unit with gas.
Conventional gas purging devices comprise in a first variant a compressor and a membrane dryer for air preparation and are generally configured for a significantly higher volume flow. In this instance, purging gas is drawn from the environment via an air preparation unit, prepared and directed through the laser resonator and the pump unit and discharged into the environment again at the end. The purging gas is permanently drawn from the environment and must therefore also be continuously cleaned. It is disadvantageous that the components are expensive and susceptible to wear.
In a second variant, purging gas from bottles having a defined quality, for example, nitrogen, is used. This is permanently drawn from the bottle, prepared, directed through the laser resonator and the pump unit and discharged to the environment again at the end.
A laser resonator having gas purging is disclosed in U.S. 2003/0007537 A1. This system comprises a closed housing (laser resonator), from which gas is drawn in a first step. This gas contains occurrences of contamination, such as, for example, water vapour, organic compounds and small particles. In order to remove these occurrences of contamination, the gas is guided in a second step through a preparation system in which the cleaning is carried out in various steps in the following sequence: firstly, the gas is passed through a first medium, for example, silica gel, in order to filter the water vapour. Afterwards, the gas passes through an organic filter. There finally follows a particle filter, which serves to separate particles. The cleaned gas is then supplied to the closed housing (laser resonator) again in a third step. The entire system is operated at ambient pressure. Furthermore, the system makes provision for a regeneration of the water vapour filter with dry gas which can be supplied to the filter and discharged from the filter via a separate line.
The laser device known from U.S. 2003/0227957 A1 mentioned in the introduction comprises a laser resonator, which is purged by means of a purging gas, such as, for example, air. The purging gas is guided in a closed circuit, in which cleaning devices are also provided in order to clean the purging gas, the purging gas pressure in the laser resonator being maintained at ambient pressure. Prior to the actual laser operation, the entire gas purging system is flooded with nitrogen in order to remove contaminations present therein and to reduce the oxygen content, and afterwards purged with the purging gas.
A disadvantage of these known gas purging systems is that they are operated at ambient pressure. Hermetically sealing a closed housing is a great challenge and cannot always be implemented. It is thus possible, in the event of leaks, for contamination from the environment to enter the gas purging system and to be able to be deposited on laser components without being filtered from the purging gas beforehand, whereby the stability of the laser operation may be impaired.